Liquid-cooling system for rotary-piston mechanisms

ABSTRACT

In a liquid-cooling system for rotary piston-type mechanisms comprising a plurality of series-connected passes in areas of which the cooling liquid is capable of defining with the walls of the cooling system passageways a fluidtight chamber where entrapment of air and/or vapor can occur, the provision of passageway means disposed to communicate each of the fluidtight chambers with other portions of the liquid-cooling flow path in which cooling liquid is free flowing and of lesser pressure to thereby vent the fluidtight chamber areas and prevent air and/or vapor entrapment.

United States Patent Charles Jones Hillsdale, NJ.

Sept. 3, 1969 Mar. 30, 1971 Curtiss-Wright Corporation Inventor Appl. No. Filed Patented Assignee LIQUID-COOLING SYSTEM FOR ROTARY- PISTON MECHANISMS 19 Claims, 7 Drawing Figs.

US. Cl 418/83, 123/4129, 123/4154 Int. Cl F01c 21/06,

F01 p 3/00 Field of Search 103/130;

[56] References Cited UNITED STATES PATENTS 3,007,460 11/1961 Bentele et a1. 123/845 3,102,516 9/1963 Gist et al 123/8(CC) 3,134,537 5/1964 Bentele et al. 123/8(CC) 3,289,647 12/1966 Turner et a1. 123/8(CC) Primary Examiner-Carlton R. Croyle Assistant Examiner-Wilbur J. Goodlin Attorneys-Arthur L. Frederick and Victor D. Behn ABSTRACT: In a liquid-cooling system for rotary-piston type mechanisms comprising a plurality of series-connected passes in areas of which the cooling liquid is capable of defining with the walls of the cooling system passageways a fluidtight chamber where entrapment of air and/or vapor can occur, the provision of passageway means disposed to communicate each of the fluidtight chambers with other portions of the liquidcooling flow path in which cooling liquid is free flowing and of lesser pressure to thereby vent the fluidtight chamber areas and prevent air and/or vapor entrapment.

Patented March 30, 1971 4 Sheets-Sheet 1 CHARL ES JONES AT TORNE Y Patented March 30, 1971 3,572,984

4 Sheets-Sheet 2 26 FIG? 27 III a l II/II 2 22 r 3 4 2 9 g b 9 FIG.4 i l I INVILN'I UR 29 28 46 5o 29 CHARLES JONES ATTORNEY Patented March 30, 1971 4 Sheets-Sheet S m @Nk INVliN'I ()R CHARL ES JONES A T TORNE Y Patented March 30, 1971 3,572,984

4 Sheets-Sheet 4 FIG. 7

I NVIiN'IUR. CHARLES JONES ATTORNEY LlQlJi'ill-COGLMG SYSTEM lFGlii ROTARY-WESTON MEHSM$ BACKGROUND OF THE INVENTION This invention relates to rotary-piston mechanisms an more particularly to an improved liquid cooling system for rotary piston mechanisms.

in rotary-piston mechanisms of the combustion engine type, such as disclosed in the US. patents to Bentele et al.; US. Pat, No. 3,007,460; Bentele, US. Pat. No. 3,062,435; and Turner et al., US. Pat. No. 3,289,647, having a cooling system comprising a plurality of liquid passes extending substantially parallel to the axis of engine drive shaft and connected together for series flow therethrough by return bends or distribution manifolds, it has been found that air and/or vapor pockets tend to develop in various portions of the liquid-cooling passageways. The air entrapment occurs upon the initial filling or addition of cooling liquid to the cooling system, while vapor entrapment occurs when some of the liquid, such as water, upon absorption of heat, is vaporized (converted to steam when water is the cooling fluid) and disentrains from the liquid. This entrapment of air and/or vapor restricts and interferes with proper distribution of cooling liquid flow and thereby prevents effective cooling of the engine housing in the areas of air and/or vapor entrapment which, in turn, results in undue heat stress on the housing and fracture thereof.

This vapor and/or air blockage problem is of particular concern in installations, such as marine or aircraft conveyances, where the engine is mounted or operates for sustained periods in a position inclined from a usual or normal upright position; as for example, a position achieved by rotation about the longitudinal axis of the rotorshaft or endwise, fore-and-aft tilting of the engine so that the longitudinal axis of the rotor shaft extends at an angle with respect to a horizontal plane More specifically, in marine installations, 'the engine is usually mounted witlithe longitudinal axis of the rotor shaft extending at an angle, as for example, about 20, from a horizontal plane so that the liquid in the passageways of the cooling system defines with various ribs or webs, forming the passageways, fluidtight chambers. In the application of the engines to air craft use, the engine position, in addition to being mounted at an angle with regard to what might be designated the upright position, will be operated at various positions for sustained periods as, for example, in ascending or descending attitudes of flight.

It is, therefore, an object of this invention to provide, in a rotary piston-type mechanism, a liquid-cooling passageway system in which air and/or vapor entrapment is obviated.

It is a further object of the present invention to provide, in a rotary piston-type mechanism, a liquid-cooling passageway system, having a plurality of passageways arranged to provide a plurality of parallel, series-connected passes, capable of effcctively cooling the mechanism regardless of positional attitude of the mechanism during use of the mechanism.

A still further object of this invention is to provide, in a rotary piston-type mechanism having a cooling liquid system comprising a plurality of series-connected parallel passes formed, at least in part, by ribs or webs, means for obviating air and/or vapor entrapment in the liquid-cooling system regardless of the disposition of the mechanism during use thereof.

A feature of this invention is the provision, in a liquid-cooling system having a plurality of passes, of passageway means communicating the areas of the liquid-cooling passageway system where entrapment of air and/or vapor would potentially occur with other areas of the liquid-cooling passageways system where the cooling liquid is free flowing and a lower pressure to thereby permit air and/or vapor to flow from the areas of potential entrapment.

SUMMARY OF THE INVENTION Accordingly, the present invention contemplates, in a rotarry-piston mechanism having a liquid-cooling system constructed and arranged to provide a plurality of parallel, seriesconnected, liquid passes, an improved cooling system comprising vent passageway means disposed to communicate each area of the liquid-cooling passageway system where the liquid is capable of defining with the walls of the passageway system a fluidtight chamber in which entrapment of air and/or vapor can occur, with another area of the liquid-cooling passageway system which is at a lower liquid pressure and free flowing, to conduct air and/or vapor from the area of potential entrap ment.

Each of the vent passageway means is of relatively small size so that no significant adverse efiect on the cooling liquid flow through thepassageway systemoccurs. It has been found that in certain areas only a negligible amount of cooling liquid is bypassed, through the vent passageway means, and therefore, such vent means does not interfere with effective cooling of the mechanism.

BRIEF DESCRJPTlON OF THE DRAWlNG The invention will be more fully understood from the following detailed description thereof when considered in connection with the accompanying drawing wherein several embodiments of the invention are illustrated by way of example and, in which:

FIG. 1 is an elevational view of a rotary-piston mechanism mounted at an acute angle with respect to a horizontal plane with parts broken away to show portions of the improved cooling liquid passageway system according to one embodiment of this invention;

FIG. 2 is a cross-sectional view taken substantially along line 2 2 of FIG. 1;

FIG. 3 is a fragmentary sectional view taken substantially along line 3-3 of FIG. 2;

FIG. 4 is a fragmentary sectional view taken substantially along line 4-4 of FIG. 2;

FIG. 5 is an elevational view of a rotary-piston mechanism having three rotary-pistons with an improved cooling liquid passageway system according to this invention;

HO. 6 is a view in cross section taken substantially along line 6-6 of FIG. 5; and

FIG. 7 is a fragmentary sectional view taken substantially along line 7-7 of FIG. 6.

Now referring to the drawings and, more particularly, to FIGS. 1 to 4, inclusive, the reference number 10 generally designates a rotary-piston mechanism of the type fully disclosed in the US. Pats. to Bentele et al., US. Pat. No. 3,007,460; Bentele, US. Pat. No. 3,062,435; and Turner et al., US. Pat. No. 3,289,647. Since the structure and function of the rotary-piston mechanism 1!) herein shown in the aforementioned drawings is fully disclosed, mechanism 10 will only be briefly described.

The rotary-piston mechanism 10, as shown in FIGS. 1 to 4, comprises two triangular-shaped pistons 12 rotatively mounted within epitrochoidal-shaped cavities or chambers 14 to receive or transmit rotation to a shaft 16. The shaft 16 is journaled for rotation in a sectional casing which comprises two abutting housing sections 18, an intermediate housing section 20, and opposite end wall sections 22. The casing sections 13, 20 and 22 are secured together in abutting relationship by a plurality of tie bolts 2d, thus defining chambers M. To provide for cooling of rotary-pistonmechanism iii, a liquid-cooling system of the type, such as disclosed in the aforementioned U.S. Pats, is provided.

The liquid-cooling system comprises a plurality of liquid flow passes 25, 26, 27 and 28, extending substantially parallel to the axis of shaft 16 and in communication with each other for series flow thcrethrough by way of return bend cavities or manifolds 7,9. The passes 25, as, 27, 28 and manifolds w are formed within casing sections ill, 20 and 22 by spaced ribs and webs which are preferably integrally cast in the sections. To provide for the introduction of cooling liquid such as water, into rotary-piston mechanism i and withdrawal of heated cooling liquid from the rotary-piston mechanism, intermediate section 22b is provided with ribs 39 which define an inlet port 3i and an outlet port 32, partially surrounding the inlet port (see F116. 4). The inlet port 31 and outlet port 32 are in communication with inlet and outlet passageways 34 and as of a connecting manifold 38, passageways 34 and 36 being connected by means, not shown, to a liquid heat exchanger, such as an air-cooled radiator, not shown. As shown in FIGS. 2 and 4, inlet port 37. communicates with the passageways forming pass 25 in each of the housing sections 18 to conduct cooling liquid in two streams to each housing section, while outlet port 31 is in communication with the passageways forming pass 28 to receive the heated cooling fluid from each of the housing sections to thereby provide for two balanced cooling liquid flow paths. As best shown in FIGS. l and 2, intermediate section is provided with two circumferentially spaced, radially extending webs 40 and 42 and a dividing rib or wall 43 which define two of the manifolds 2h, hereinafter referred to as the intermediate manifolds 29, hereinafter reterred to as the intermediate manifolds. As best shown in H6. 3, each of the housing sections 18 is provided with a rib 44 which abuts at one end inlet rib 30 and a rib as in the adjacent end wall secton 22 to thereby form, with web ill and abutting ribs in housing sections 18, inlet manifolds 29 (see hi6. 2) in intermediate section 29 and flow passes 25.

The cooling system, as heretofore described, is a flooded" system which for heat transfer efficiency and effectiveness requires the cooling liquid to fiow adjacent all the surfaces defining the passes and manifolds of the cooling system. However, in the use and operation of rotary-piston mechanism ill, for sustained periods of time, as in marine propulsion applications, with the longitudinal axis X-X extending at an angle with respect to a horizontal plane (as is illustrated in FlGS. l and 3) various points in the cooling liquid system have a tendency to entrap air upon filling the system or entrap liquid vapor which restricts free flow of cooling liquid. These restrictions to cooling liquid tlow result in localized points of thermal stress in the casing walls and the resultant fracture thereof. To obviate areas of air and/or vapor entrapment in the liquid cooling system, the present invention contemplates passageway means communicating the areas of entrapment with other areas of the liquid-cooling system which are free flowing and at a lesser pressure than the liquid stream at the areas of entrapment.

ln rotary-piston mechanism 30 as shown in FIGS. 1 to 4, one of the several areas of air and/or vapor entrapment in the coolingsystern is at dividing rib 43 of intermediate housing section Zll. This potential fluidtight entrapment chamber is indicated by the letter A and is defined by a liquid level L and the contiguous walls of rib 43, web 46) and the inner peripheral surfaces of the sectional casing. As best shown in FIGS. 1 and 2, a vent opening 48 is provided in dividing rib 43 to communicate the potential fluidtight chamber A with the next adjacent intermediate manifold 29 through which liquid coolant is free flowing and at a slightly lesser pressure. The vent opening 4% serves to conduct any air or vapor which would, in absence of the opening 48, become trapped, from chamber A to intermediate manifold 2@ so that no buildup or accumulation of air or vapor can occur. To achieve this function, vent opening 43 is of relatively small dimensions so that no significant adverse effect on the cooling liquid flow occurs, such as excessive passage of liquid through opening 48 thereby upsetting the balance of liquid flow. This improvement is of particular importance in the area of chamber A when the rotary-piston mechanism 10 is an internal combustion engine because this portion of the cooling system is in the area of fuel combustion where effective cooling of the casing is essential to prevent thermal stress damage to the casing.

As best shown in FIGS. 3 and 4;, another area of air and/or vapor entrapment in the cooling system of mechanism it) is in a chamber B formed partly in the liquid pass and manifold 29 of housing section 13 and end wall section 22, respectively, which sections are at a higher elevation with respect to a horizontal plane than the other housing and end wall sections (see MG. 1). This potential entrapment chamber B is defined by a liquid level L and the walls defining pass 2d and manifold 29. To eliminate entrapment chamber B, a vent opening 59, in accordance with this invention, is disposed in rib is to communicate liquid pass 25, at the potential area of entrapment, with liquid pass 2% which conducts the heated cooling liquid from manifold 29 in end wall section 22 to outlet port 32. Since liquid pass 28 is the last pass before discharge of the liquid coolant, it is at a lesser pressure than the fluid pressure in inlet pass 25 so that any air and/or vapor is passed from the potential entrapment chamber B to outlet pass 2%.

An additional area of air and/or vapor entrapment in the cooling system of mechanism w is in outlet pass 28 and manifold 2h adjacent to potential entrapment chamber B. As best shown in FIGS. 2 and 3, this potential entrapment chamber Q, in absence of the present invention, would be defined by a liquid level L (FIG. 2) and the inner walls forming manifold 29 and pass 28 in end wall section 22 and housing section 18, respectively. The potential entrapment chamber C is eliminated according to this invention, by a vent opening 52 in which is secured one end of a vent tube 54. The opposite end of vent tube 54 is connected to connecting manifold 38 so as to communicate with outlet passageway 36. The vent opening 52 and vent tube 54 function to conduct any air and/or vapor which may tend to collect in potential entrapment chamber C to the heated cooling liquid which is flowing via outlet passageway 36 to a heat exchanger (not shown) and is therefore at a lower pressure than the liquid in the area of chamber C.

it is believed now readily apparent that by providing at areas of potential air and/or vapor entrapment in the cooling system of rotary-piston mechanism 10, partial blockage of coolant liquid is avoided an an efiicient and effective liquid-cooling system is attained.

in FIGS, 5, 6 and 7 is shown another rotary-piston mechanism 60 which is particularly suitable as an aircraft engine. Mechanism 60 differs principally from the rotary-piston mechanism ll) in that it has more than two rotary-pistons and has a modified liquid-cooling system wherein a connecting manifold is formed integral with the sectional casing to conduct and receive cool and liquid to and from the cooling liquid passageways surrounding each rotary-piston. The areas of potential air and/or vapor entrapment in the cooling system of mechanism 60 is alleviated, in accordance with this invention, by vent means similar to those described for rotary-piston mechanism ill.

As shown in FIG. 5, rotary-piston mechanism 60 comprises a sectional casing in which three or more rotary-pistons 61 are supported for rotation and transmit to or receive rotation from a shaft 62. The sectional casing has, in part, three or more housing sections 63, corresponding in number to the number of pistons, which sections have an epitrochoidal inner peripheral surface. The sectional casing also includes intermediate sections 64 disposed between adjacent housing sections 63 and end wall sections 66 disposed in abutment against each of the endmost housing sections. The housing sections 63, intermediate sections 64 and end wall sections 66 are secured together in tight abutting relationship by tie bolts 68.

A liquid-cooling system is provided for mechanism 60, which system includes for each rotary-piston 61 a plurality of flow passes arranged peripherally in each housing section 63 and extending parallel to the longitudinal axis of shaft 62. The flow passes are connected together for series flow of liquid therethrough by manifolds 7ll and 72 formed in end wall sections 66 and intermediate sections 64, respectively. Similarly to rotary-piston mechanism 10, the flow passes and the manifolds of mechanism till are formed by webs or ribs preferably cast integrally with the sectional casing elements. Each intermediate section 64 has an inlet port 74 and an adjacent outlet port 76, which as best shown in MG. 6 are partially formed by a partition 75. Also integrally formed with each intermediate section 6 5 is an inlet conduit 73 and an outlet conduit 84) which communicate with the associated inlet port M and outlet port 76, respectively. Inlet conduit 78 is in alignment and communication with an inlet passageway 82 formed in each of the housing sections 63, while outlet conduit hill is in alignment and communication with an outlet passageway 84. formed in each of the housing sections 63. End wall section 66 disposed on the right of the mechanism, as viewed in FIG. 5, is provided with an inlet port (not shown) and an adjacent outlet port d6 which communicate, respectively, with inlet passageway 82 and outlet passageway 8% in the abutting housing section 63. When the housing sections as, intermediate sections dd and end wall sections as are assembled as shown in FIGS. 5 and 6, aligned inlet conduits 78 and inlet passageways 82 form a cooling liquid inlet manifold while aligned outlet conduits dll and outlet passageways 34 coast to .form a cooling liquid outlet manifold extending parallel to the inlet manifold. it is thus apparent that mechanism 60 is provided with an integral cooling liquid inlet and outlet manifold which provides for flow of cooling liquid to each of the inlet ports '74, including the inlet port (not shown) in end wall section as, and receives flow of heated cooling liquid from each of the outlet ports '76 and 86.

As in the rotarypiston mechanism 10, use or operation of rotary-piston mechanism 6d at an inclination to a horizontal plane, wherein the right-hand end portion of the mechanism, as viewed in H6. 5,' is lower than the opposite end portion, various areas of potential air and/or vapor entrapment exist. One area of potential air and/or vapor entrapment is designated by the letter D. Each of these potential entrapment chambers D in each of the intermediate sections 64 is eiiminated, in accordance with this invention, by a restricted passageway @8 by which air and/or vapor is vented to the outlet port '76 of the liquid coolant flow system of the next adjaccnt rotary-piston 611. Another area of air and/or vapor blockage is in end wall section 66 which potential chamber is designated by the letter E. This potential entrapment chamber E is relieved by a vent port 90 which communicates with the outlet manifold.

As shown in FIGS. 5 and 6, another area of potential air and/or vapor entrapment is in the upper portionsof inlet conduits 7d and passageways 82 of the inlet manifold and outlet conduits 8b and outlet passageways 84 of the outlet manifold. These areas are designated by the letter F and are vented by a vent means comprising a recess 92 in end wall section 66 and a vent passageway consisting of aligned vent holes 94 in housing and intermediate sections 63 and dd and a vent conduit 96 which is connected, at one end, to end wall section 66 and, at the opposite end, to a heat exchanger (not shown), such as a radiator. This vent means also serves to relieve a potential area of blockage in the right-hand end portion of the inlet manifold passage adjacent end wall section 66, as viewed in FIG. 5, when mechanism dd is tilted along the longitudinal axis of shaft 62 with the right-hand end wall in an elevated position above the level of opposite end wall section 66.

A still further area of potential vapor air/or entrapment is shown in 6 and indicated by the letter G. This potential entrapment chamber (3 is similar to potential entrapment chamber A and is vented by a vent port 98, similar to vent opening dd of mechanism W. In MG. '7 is shown an alternative means of venting chamber G. The alternative vent means comprises a vent passageway formed by a recess ltltl in the end face of intermediate housing section 6 and the end face of the abutting housing section 63 which vent passageway communicates chamber G with the adjacent outlet manifold it is believed now readily apparent that the present invention provides an improved liquid-cooling system for a rotarypiston mechanism wherein partial blockage of the liquid-cooling ilow path by vapor and/or air entrapment has been obviated so that the rislt of fracture of the mechanism components due to excess thermal stresses has been eliminated.

lclaim:

1. An improved liquid-cooling system for a rotary-piston mechanism having means forming a liquid flow passageway means including aplurality of series-connected parallel passes for conducting liquid at progressively decreasing pressures in the direction of flow and in which passageway means the liquid therein tends to define with a portion of the walls of the passageway means at least one potential fluidtight chamber, the improvement comprising a conduit means for the potential fiuidtight chamber communicating the iluidtight chamber with another portion of the passageway means which is at the same or a lesser pressure than said fluidtight chamber to corn duct from such fluidtight chamber gaseous fluid and thereby prevent the entrapment of such gaseous fluid and the blockage of a portion of the passageway means.

2. The apparatus of claim 1 wherein said conduit means extends from its associated potential fluidtight chamber to the nearest adjacent area of the passageway means of lower pressure to thereby provide a relatively low pressure drop therethrough.

3. The apparatus of claim 1 wherein said conduit means is vent of restricted flow area to provide negligible cooling fluid flow therethrough.

4. The apparatus of claim 1 wherein said means forming a liquid flow passageway means is the housing of the rotarypiston mechanism constructed and arranged to provide integral passageway means including said plurality of series-com nected parallel passes.

d. The apparatus of claim 1 wherein the longitudinal axis of the passes extend substantially parallel to the axis of rotation of the mechanism and the mechanism is supported with said axis of rotation extending at a substantial acute angle with respect to a horizontal plane.

6. The apparatus of claim 5 wherein said substantial acute angle is about 20.

7. The apparatus of claim l wherein the passageway means further includes retum-bend means for connecting said plurality of passes together for series flow therethrough and at least a portion of said return-bend means tends to define with the liquid therein said potential fluidtight chamber.

8. The apparatus of claim 1 wherein said liquid flow passageway means includes a radiator having an inlet and said conduit means communicates said fluidtight chamber with the inlet of said radiator.

9. The apparatus of claim 1 wherein said liquid flow passageway means includes an outlet manifold and said conduit means communicates said fluidtight chamber with the outlet manifold.

Ill. The apparatus of claim 1 wherein said rotarypiston mechanism comprises a rotor shaft for supporting at least one rotor for rotation in a housing and wherein said passes extend in said housing substantially parallel to the axis of rotation of said rotor shaft.

ll. The apparatus of claim 1 wherein said mechanism includes a housing comprising a plurality of abutting sections, the housing sections having spaced ribs which abut adjacent housing sections to define portions of the passageway means and wherein conduit means is formed by a recess in the abutting surface of a rib and the abutting housing section.

12. In a rotary-piston combustion engine comprising a housing, a plurality of rotors supported for rotation in a housing by a rotor shaft, a cooling system comprising:

a. a plurality of spaced webs constructed and arranged in said housing to define a liquid-cooling flow path comprising a plurality of parallel passageways interconnected by distribution manifolds for providing series flow of liquid therethrough at progressively decreasing pressures;

b. said housing having a liquid inlet means communicating with a source of cooling liquid and said plurality of passageways to conduct cool liquid to the latter for ab sorption of heat from the housing;

. said housing having an outlet means in communication with the plurality of passageways and with said source of cooling liquid to receive from the pmsageways heated liquid and conduct the same to the said source for coolmg;

d. vent means disposed in said webs at points where the liquid in said liquid cooling flow path tends to define with a portion of the adjacent walls of defining the liquid cooling flow path a potential-fluid tight chamber;

e. said vent means communicating the associated potential fluidtight chamber with another portion of the cooling flow path which has free-flowing liquid at the same or lower pressure therein to provide for flow of gaseous fluid from the potential fluidtight chamber to said another portion of the cooling flow path.

H3. The apparatus of claim 12 wherein said housing comprises a plurality of abutting sections and wherein said vent means comprises a recess in the surface of a web of one housing section which abuts the surface of the adjacent housing section to thereby bring into communication the cooling fluid flow path on opposite sides of said web.

E4. The apparatus of claim 12 wherein said source of cooling liquid is a heat exchanger capable of cooling the liquid and having an expansion vapor space which is vented to atmosphere.

l. An improved liquid cooling system for a rotary-piston mechanism having a plurality of abutting piston-cylinder assemblies each of which is provided with means forming a cooling iquid passageway means comprising inlet and outlet ports interconnected by a plurality of series connected parallel passageways, the inlet and outlet ports of each piston-cylinder assembly being in communication with an inlet and outlet cooling liquid manifold, the improvement comprising the provision of fluid flow vent means communicating the passageway means of one piston-cylinder assembly at a point where entrapment of air or vapor tends to occur with the passageway means of the adjacent piston-cylinder assembly at a point where the cooling liquid is free flowing and at the same or lesser pressure.

to. The apparatus of claim 15 wherein said fluid flow vent means is defined by a groove in the end face of one pistoncylinder assembly and the abutting surface of the next adjacent piston-cylinder assembly.

17. In a rotary-piston mechanism comprising a plurality of adjacent pistons confined for rotation within housing elements interconnected by abutting intermediate housing elements, and opposite end housing elements, the piston and intermediate housing elements and the end housing elements being constructed and arranged to provide in abutment with each other a separate cooling liquid passageway means surrounding each rotary piston and communicating at one end with a cooling liquid inlet manifold and at the opposite end with a cooling liquid outlet manifold, an improvement comprising vent means in said intermediate housing element communicating the passageway means associated with one rotary piston at a point where entrapment of air or vapor tends to occur with the passageway means associated with the next adjacent rotary piston at a point where the cooling liquid is free flowing at the same or lesser pressure.

28. The apparatus of claim 17 wherein said vent means is at least partially defined by a groove in one of the end faces of the abutting rotary piston housing and intermediate housing.

L9. The apparatus of claim 17 wherein vent means is provided in the inlet manifold to vent the same to a lower pressure area. 

1. An improved liquid-cooling system for a rotary-piston mechanism having means forming a liquid flow passageway means including a plurality of series-connected parallel passes for conducting liquid at progressively decreasing pressures in the direction of flow and in which passageway means the liquid therein tends to define with a portion of the walls of the passageway means at least one potential fluidtight chamber, the improvement comprising a conduit means for the potential fluidtight chamber communicating the fluidtight chamber with another portion of the passageway means which is at the same or a lesser pressure than said fluidtight chamber to conduct from such fluidtight chamber gaseous fluid and thereby prevent the entrapment of such gaseous fluid and the blockage of a portion of the passageway means.
 2. The apparatus of claim 1 wherein said conduit means extends from its associated potential fluidtight chamber to the nearest adjacent area of the passageway means of lower pressure to thereby provide a relatively low pressure drop therethrough.
 3. The apparatus of claim 1 wherein said conduit means is vent of restricted flow area to provide negligible cooling fluid flow therethrough.
 4. The apparatus of claim 1 wherein said means forming a liquid flow passageway means is the housing of the rotary-piston mechanism constructed and arranged to provide integral passageway means including said plurality of series-connected parallel passes.
 5. The apparatus of claim 1 wherein the longitudinal axis of the passes extend substantially parallel to the axis of rotation of the mechanism and the mechanism is supported with said axis of rotation extending at a substantial acute angle with respect to a horizontal plane.
 6. The apparatus of claim 5 wherein said substantial acute angle is about 20*.
 7. The apparatus of claim 1 wherein the passageway means further includes return-bend means for connecting said plurality of passes together for seRies flow therethrough and at least a portion of said return-bend means tends to define with the liquid therein said potential fluidtight chamber.
 8. The apparatus of claim 1 wherein said liquid flow passageway means includes a radiator having an inlet and said conduit means communicates said fluidtight chamber with the inlet of said radiator.
 9. The apparatus of claim 1 wherein said liquid flow passageway means includes an outlet manifold and said conduit means communicates said fluidtight chamber with the outlet manifold.
 10. The apparatus of claim 1 wherein said rotary-piston mechanism comprises a rotor shaft for supporting at least one rotor for rotation in a housing and wherein said passes extend in said housing substantially parallel to the axis of rotation of said rotor shaft.
 11. The apparatus of claim 1 wherein said mechanism includes a housing comprising a plurality of abutting sections, the housing sections having spaced ribs which abut adjacent housing sections to define portions of the passageway means and wherein conduit means is formed by a recess in the abutting surface of a rib and the abutting housing section.
 12. In a rotary-piston combustion engine comprising a housing, a plurality of rotors supported for rotation in a housing by a rotor shaft, a cooling system comprising: a. a plurality of spaced webs constructed and arranged in said housing to define a liquid-cooling flow path comprising a plurality of parallel passageways interconnected by distribution manifolds for providing series flow of liquid therethrough at progressively decreasing pressures; b. said housing having a liquid inlet means communicating with a source of cooling liquid and said plurality of passageways to conduct cool liquid to the latter for absorption of heat from the housing; c. said housing having an outlet means in communication with the plurality of passageways and with said source of cooling liquid to receive from the passageways heated liquid and conduct the same to the said source for cooling; d. vent means disposed in said webs at points where the liquid in said liquid cooling flow path tends to define with a portion of the adjacent walls of defining the liquid cooling flow path a potential-fluid tight chamber; e. said vent means communicating the associated potential fluidtight chamber with another portion of the cooling flow path which has free-flowing liquid at the same or lower pressure therein to provide for flow of gaseous fluid from the potential fluidtight chamber to said another portion of the cooling flow path.
 13. The apparatus of claim 12 wherein said housing comprises a plurality of abutting sections and wherein said vent means comprises a recess in the surface of a web of one housing section which abuts the surface of the adjacent housing section to thereby bring into communication the cooling fluid flow path on opposite sides of said web.
 14. The apparatus of claim 12 wherein said source of cooling liquid is a heat exchanger capable of cooling the liquid and having an expansion vapor space which is vented to atmosphere.
 15. An improved liquid cooling system for a rotary-piston mechanism having a plurality of abutting piston-cylinder assemblies each of which is provided with means forming a cooling liquid passageway means comprising inlet and outlet ports interconnected by a plurality of series connected parallel passageways, the inlet and outlet ports of each piston-cylinder assembly being in communication with an inlet and outlet cooling liquid manifold, the improvement comprising the provision of fluid flow vent means communicating the passageway means of one piston-cylinder assembly at a point where entrapment of air or vapor tends to occur with the passageway means of the adjacent piston-cylinder assembly at a point where the cooling liquid is free flowing and at the same or lesser pressure.
 16. The apparatus of claim 15 wherein said fluid flow vent means is defined by a groove in the end face of one pistOn-cylinder assembly and the abutting surface of the next adjacent piston-cylinder assembly.
 17. In a rotary-piston mechanism comprising a plurality of adjacent pistons confined for rotation within housing elements interconnected by abutting intermediate housing elements, and opposite end housing elements, the piston and intermediate housing elements and the end housing elements being constructed and arranged to provide in abutment with each other a separate cooling liquid passageway means surrounding each rotary piston and communicating at one end with a cooling liquid inlet manifold and at the opposite end with a cooling liquid outlet manifold, an improvement comprising vent means in said intermediate housing element communicating the passageway means associated with one rotary piston at a point where entrapment of air or vapor tends to occur with the passageway means associated with the next adjacent rotary piston at a point where the cooling liquid is free flowing at the same or lesser pressure.
 18. The apparatus of claim 17 wherein said vent means is at least partially defined by a groove in one of the end faces of the abutting rotary piston housing and intermediate housing.
 19. The apparatus of claim 17 wherein vent means is provided in the inlet manifold to vent the same to a lower pressure area. 